The long term objective of this research program is to define the structure, metabolism and function of proteoglycans (mucopolysaccharides) as these parameters reflect the remodeling of connective tissue in health and disease. The research efforts proposed for 6/1/84-5/31/89 will emphasize studies on the cellular mechanisms involved in the uptake, intracellular translocation, and secretion of lysosomal enzymes and proteoglycans. Major emphasis will continue to be placed on the role of the phosphomannosyl receptor in the uptake and intracellular transport and secretion of lysosomal enzymes. The model system used for these studies utilizes homogeneous Beta-galactosidase and skin fibroblasts derived from patients with generalized gangliosidosis (GM1) which lack this lysosomal enzyme. Attempts will be made to establsh: 1) how the receptor aggregate is assembled in the endoplasmic reticulum and/or golgi membranes; 2) the structural features required for the binding of lysosomal enzymes to the phosphomannosyl receptor and packaging into lysosomes; 3) how the receptor is recycled to the golgi and/or the cell surface; and 4) if therapeutic agents coupled to the phosphomannosyl recognition marker can be efficiently and specifically targeted to cells and can correct or alleviate abnormal metabolism (remodeling) of connective tissue. In parallel studies the mechanism for the uptake of proteoglycans and proteoglycan derivatives by cells during connective tissue remodeling will be investigated. The results of studies in this laboratory provide strong support for the existence of specific recognition markers and binding proteins (receptors) for proteoglycans in a number of connective tissue-associated cell types. Efforts will be initiated to isolate and characterize each component of the recognition system. These studies will include attempts to establish if the uptake of proteoglycans by cells represents a simple salvage pathway or possibly participates in the control of connective tissue remodeling. Experimentation will be restricted largely to the binding and uptake of the well-defined protein-chondroitin 4-S04 complex by connective tissue-associated cell types and those in liver. The above-described studies will involve the use of "state of the art" tissue culture, radioisotopic, electrophoretic, immunochemical and cytochemical techniques.